When is the right time to change therapy? An observational study of the time to response to immunosuppressive drugs in systemic lupus erythematosus.

Objectives: To analyse the response to immunosuppressants (IS) in extrarenal flares of SLE to determine the most appropriate timing during follow-up for a change in therapeutic strategy.

Methods: Observational cohort study including a total of 81 patients with SLE with extrarenal flares requiring a change in IS over the period 2015-2022. Baseline clinical variables were described, and follow-up data at 1, 3, 6 and 12 months time-points were collected.

Results: Among patients flaring that achieved lupus low disease activity state (LLDAS5) at 12 months of follow-up, we identified two subgroups ('late responders' and 'early responders'), which showed no significant differences in demographic characteristics, baseline clinical data, cumulative dosage of glucocorticoids or type of IS. Cox model analysis revealed a significant association of a change in IS (p=0.019) and achieving LLDAS5. Contingency table analysis indicated a significant relationship (p=0.004) between IS change at 6 months and individuals achieving LLDAS5 and remission at 12 months.

Conclusions: Our findings suggest that clinical improvement of extrarenal flares typically occurs within 6 months of initiating IS. This timeframe could represent an appropriate timing to evaluate the response in a treat-to-target approach in SLE.